As known, a variety of types of exoskeleton apparatus exist for measuring the position and/or the orientation of an user's limb and that can reflect a force feedback at determined points. As force feedback is meant the replication on the user of “haptic” sensations reflecting handling forces of real or virtual objects.
If the objects are real and the user interacts directly with a physical environment, then Teleoperation is involved, whereas if such objects and the whole environment are created by computers using electronic displays, than Virtual Reality is involved.
Teleoperation provides bilateral communication between a manipulator (robot) operating in a remote environment (slave) and an interface apparatus (master) controlled by the user. This allows to give the robot the capacity of carrying out not foreseeable high skill operations on not structured objects and environments, i.e. whose shape, size and spatial disposition are unknown a priori.
Furthermore, since the master and the slave can communicate even if located at considerable distance (for example by means of satellite broadcasting) operations can be carried out in absolutely safe conditions at places that are dangerous to humans, such as in the maintenance of nuclear sites or of satellites.
Virtual reality can be defined as an interactive and immersive experience in a simulated environment. The fields of application of Virtual reality are many. Among them the following can be cited: simulation, training, medicine, entertainment, teaching, design, etc.
A variety of exoskeleton interface apparatus exist for upper limbs of humans.
For example, a first type of interface apparatus that is used as master in a teleoperation system is “Arm Master” of Sarco Inc. It has 10 freedoms (arm+hand) and is capable of reflecting a force on 3 fingers. The actuating system is hydraulic so that it has the advantage of having a high passband, but it has the drawback of having a big encumbrance and a low “transparency of use” (high friction and high reflected mass on the user).
Then, a type of exoskeleton exists with parallel kinematics developed by the Korea Institute of Science and Technology. The choice of a parallel kinematics has the advantage of a good stiffness, but the mobility of the shoulder and of the elbow are limited. Six linear actuators are provided (three for the arm and three for the forearm) using DC motors and ball recirculations. This solution reduces the reversibility rate and then the transparency of use of the device.
Furthermore, Southern Methodist University obtained a pneumatically actuated interface apparatus with four freedoms called “the Haptic Arm”. In this case the sensorisation is obtained by pressure sensors and linear position transducers. The device even if compact and light, is characterised by a low stiffness owing to the pneumatic actuation.
Normally, in the above systems the physiological axes of the arm, forearm and wrist do not coincide with the exoskeleton axes, with subsequent decrease of the actual workspace that is the intersection between the workspace of the human limbs and that of the robotic structure.
Finally, Hashimoto Lab. of Tokio disclosed an exoskeleton with seven freedoms, wherein both the angle and the torque of each joint can be determined by a sensorisation system. The transmission of the movement is carried out by a gearing. This type of transmission allows the physiological axes to coincide with the mechanical axes, but with the drawbacks of high backlash and a low rate of reversibility. In addition, since the motors are arranged on the mobile parts, the inertia reflected on the user is remarkable. Problems of safety are also caused by the fact that, being the structure closed, the introduction and the extraction of the arm it is not simple and immediate.